� 1.
Coverings of the Brain and CSF Flow
● The brain and spinal cord are covered by 3 layers:
Dura mater (outer), Arachnoid (middle), and Pia mater (inner).
● CSF (Cerebrospinal Fluid) is found in the subarachnoid space (between
arachnoid and pia).
● Functions of CSF: Cushions the brain, supports its weight, clears waste.
� CSF Production and Flow:
● Made by choroid plexus in lateral, third, and fourth ventricles.
● Flows:
Lateral ventricles → Foramina of Monro → Third ventricle →
Aqueduct of Sylvius → Fourth ventricle → Subarachnoid space →
Absorbed into blood via arachnoid villi (granulations) → Sagittal
sinus.
● Total CSF volume: 150-200 ml, renewed every 4 hours.
● Daily production: ~500 ml.
� 2. Lumbar Puncture (Spinal Tap)
● Done to collect CSF for diagnosis.
● Indications: Suspected CNS infections, subarachnoid hemorrhage, tumors.
● Contraindications: Skin infection at site, raised intracranial pressure (ICP).
● Needle inserted below spinal cord level at L3-L4 or L4-L5.
● Tests: Appearance, protein, glucose, cell count, pressure, PCR, cultures.
� 3. Normal CSF Values
Parameter Normal Range
Appearanc Clear and colourless
e
Pressure 70–180 mm H₂ O
pH 7.31
WBC 0–5 (all lymphocytes)
RBC Absent
Protein 0.2–0.4 g/L
Glucose 2.5–4.0 mmol/L (~½ of plasma glucose)
� 4. CSF Pathology
● Xanthochromia: Yellowish CSF (suggests bleeding, esp. subarachnoid
hemorrhage).
● Increased WBCs:
○ Lymphocytes ↑ → Viral or TB meningitis
○ Neutrophils ↑ → Bacterial or fungal meningitis
● Low glucose → Bacterial or TB meningitis
● High protein → Tumors or chronic inflammation
� Dissociation Types:
● Cell-Protein Dissociation: ↑ cells, normal protein → Meningitis
● Protein-Cell Dissociation: ↑ protein, normal cells → Tumor, nerve damage
� Terminologies:
● Pleocytosis = ↑ WBCs
○ Lymphocyte pleocytosis → Serous (viral/TB) meningitis
○ Neutrophil pleocytosis → Purulent (bacterial) meningitis
� 5. Hypertensive CSF Syndrome (↑ Intracranial Pressure)
Causes:
● Brain mass (tumor, abscess, hematoma)
● CSF flow blockage (hydrocephalus, meningitis, hemorrhage)
● ↑ venous pressure (venous sinus thrombosis)
● Brain swelling (ischemia, trauma)
Symptoms:
● Headache (esp. morning/night), vomiting, nausea, dizziness
● Sleepiness, irritability, confusion, seizures
Diagnostic Signs:
● Papilledema on eye exam
● MRI/CT: Enlarged ventricles
● Skull X-ray: Changes in Turkish saddle
⚠️ 6. Meningeal Syndrome (Meningitis Signs)
Occurs due to irritation of meninges (infection, hemorrhage).
Key Signs:
● Neck stiffness: Can’t bend neck forward
● Kernig’s sign: Can’t straighten knee while hip is flexed
● Brudzinski's signs:
○ Upper: Neck flexion → knees bend
○ Middle: Press pubic area → knees bend
○ Lower: Straightening one leg → opposite knee bends
Other Symptoms:
● Meningeal posture (arched back, head back, legs flexed)
● Photophobia (light sensitivity), phonophobia (sound sensitivity)
● Pain on pressure over eyeballs or nerve exits
� 7. Hydrocephalus (Water on the Brain)
● Hydrocephalus = Too much CSF in brain ventricles → pressure and swelling.
Types:
● Communicating: CSF flows between ventricles, but absorption is blocked (outside
blockage).
● Non-communicating (Obstructive): Blockage within ventricles (e.g., aqueduct
stenosis).
Causes:
● Overproduction, poor absorption, flow blockage
● Can be congenital (present at birth) or acquired
✅ Summary Table
Topic Key Points
CSF Cushions brain, produced in ventricles, clear fluid
Normal Values Clear, low WBC/protein, glucose ≈ ½ plasma
Lumbar Puncture Done at L3-L5 to sample CSF
Meningitis Viral: lymphocytes ↑; Bacterial: neutrophils ↑, glucose
↓
↑ ICP (Hypertensive Syndrome) Headache, vomiting, papilledema
Meningeal Signs Kernig, Brudzinski, neck stiffness
Hydrocephalus Ventricular dilation due to CSF accumulation
